#!/usr/bin/env python3
# isort: skip_file

import argparse
import datetime
import os
import pprint

import gymnasium as gym
import numpy as np
import torch
import wandb
from torch.utils.tensorboard import SummaryWriter

from tianshou.data import (
    Collector,
    HERReplayBuffer,
    HERVectorReplayBuffer,
    ReplayBuffer,
    VectorReplayBuffer,
)
from tianshou.env import ShmemVectorEnv, TruncatedAsTerminated
from tianshou.exploration import GaussianNoise
from tianshou.policy import DDPGPolicy
from tianshou.trainer import OffpolicyTrainer
from tianshou.utils import TensorboardLogger, WandbLogger
from tianshou.utils.net.common import Net, get_dict_state_decorator
from tianshou.utils.net.continuous import Actor, Critic


def get_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("--task", type=str, default="FetchReach-v3")
    parser.add_argument("--seed", type=int, default=0)
    parser.add_argument("--buffer-size", type=int, default=100000)
    parser.add_argument("--hidden-sizes", type=int, nargs="*", default=[256, 256])
    parser.add_argument("--actor-lr", type=float, default=1e-3)
    parser.add_argument("--critic-lr", type=float, default=3e-3)
    parser.add_argument("--gamma", type=float, default=0.99)
    parser.add_argument("--tau", type=float, default=0.005)
    parser.add_argument("--exploration-noise", type=float, default=0.1)
    parser.add_argument("--start-timesteps", type=int, default=25000)
    parser.add_argument("--epoch", type=int, default=10)
    parser.add_argument("--step-per-epoch", type=int, default=5000)
    parser.add_argument("--step-per-collect", type=int, default=1)
    parser.add_argument("--update-per-step", type=int, default=1)
    parser.add_argument("--n-step", type=int, default=1)
    parser.add_argument("--batch-size", type=int, default=512)
    parser.add_argument("--replay-buffer", type=str, default="her", choices=["normal", "her"])
    parser.add_argument("--her-horizon", type=int, default=50)
    parser.add_argument("--her-future-k", type=int, default=8)
    parser.add_argument("--training-num", type=int, default=1)
    parser.add_argument("--test-num", type=int, default=10)
    parser.add_argument("--logdir", type=str, default="log")
    parser.add_argument("--render", type=float, default=0.0)
    parser.add_argument(
        "--device",
        type=str,
        default="cuda" if torch.cuda.is_available() else "cpu",
    )
    parser.add_argument("--resume-path", type=str, default=None)
    parser.add_argument("--resume-id", type=str, default=None)
    parser.add_argument(
        "--logger",
        type=str,
        default="tensorboard",
        choices=["tensorboard", "wandb"],
    )
    parser.add_argument("--wandb-project", type=str, default="HER-benchmark")
    parser.add_argument(
        "--watch",
        default=False,
        action="store_true",
        help="watch the play of pre-trained policy only",
    )
    return parser.parse_args()


def make_fetch_env(task, training_num, test_num):
    env = TruncatedAsTerminated(gym.make(task))
    train_envs = ShmemVectorEnv(
        [lambda: TruncatedAsTerminated(gym.make(task)) for _ in range(training_num)],
    )
    test_envs = ShmemVectorEnv(
        [lambda: TruncatedAsTerminated(gym.make(task)) for _ in range(test_num)],
    )
    return env, train_envs, test_envs


def test_ddpg(args=get_args()):
    # log
    now = datetime.datetime.now().strftime("%y%m%d-%H%M%S")
    args.algo_name = "ddpg"
    log_name = os.path.join(args.task, args.algo_name, str(args.seed), now)
    log_path = os.path.join(args.logdir, log_name)

    # logger
    if args.logger == "wandb":
        logger = WandbLogger(
            save_interval=1,
            name=log_name.replace(os.path.sep, "__"),
            run_id=args.resume_id,
            config=args,
            project=args.wandb_project,
        )
        logger.wandb_run.config.setdefaults(vars(args))
        args = argparse.Namespace(**wandb.config)
    writer = SummaryWriter(log_path)
    writer.add_text("args", str(args))
    if args.logger == "tensorboard":
        logger = TensorboardLogger(writer)
    else:  # wandb
        logger.load(writer)

    env, train_envs, test_envs = make_fetch_env(args.task, args.training_num, args.test_num)
    args.state_shape = {
        "observation": env.observation_space["observation"].shape,
        "achieved_goal": env.observation_space["achieved_goal"].shape,
        "desired_goal": env.observation_space["desired_goal"].shape,
    }
    args.action_shape = env.action_space.shape or env.action_space.n
    args.max_action = env.action_space.high[0]
    args.exploration_noise = args.exploration_noise * args.max_action
    print("Observations shape:", args.state_shape)
    print("Actions shape:", args.action_shape)
    print("Action range:", np.min(env.action_space.low), np.max(env.action_space.high))
    # seed
    np.random.seed(args.seed)
    torch.manual_seed(args.seed)
    # model
    dict_state_dec, flat_state_shape = get_dict_state_decorator(
        state_shape=args.state_shape,
        keys=["observation", "achieved_goal", "desired_goal"],
    )
    net_a = dict_state_dec(Net)(
        flat_state_shape,
        hidden_sizes=args.hidden_sizes,
        device=args.device,
    )
    actor = dict_state_dec(Actor)(
        net_a,
        args.action_shape,
        max_action=args.max_action,
        device=args.device,
    ).to(args.device)
    actor_optim = torch.optim.Adam(actor.parameters(), lr=args.actor_lr)
    net_c = dict_state_dec(Net)(
        flat_state_shape,
        action_shape=args.action_shape,
        hidden_sizes=args.hidden_sizes,
        concat=True,
        device=args.device,
    )
    critic = dict_state_dec(Critic)(net_c, device=args.device).to(args.device)
    critic_optim = torch.optim.Adam(critic.parameters(), lr=args.critic_lr)
    policy = DDPGPolicy(
        actor=actor,
        actor_optim=actor_optim,
        critic=critic,
        critic_optim=critic_optim,
        tau=args.tau,
        gamma=args.gamma,
        exploration_noise=GaussianNoise(sigma=args.exploration_noise),
        estimation_step=args.n_step,
        action_space=env.action_space,
    )

    # load a previous policy
    if args.resume_path:
        policy.load_state_dict(torch.load(args.resume_path, map_location=args.device))
        print("Loaded agent from: ", args.resume_path)

    # collector
    def compute_reward_fn(ag: np.ndarray, g: np.ndarray):
        return env.compute_reward(ag, g, {})

    if args.replay_buffer == "normal":
        if args.training_num > 1:
            buffer = VectorReplayBuffer(args.buffer_size, len(train_envs))
        else:
            buffer = ReplayBuffer(args.buffer_size)
    else:
        if args.training_num > 1:
            buffer = HERVectorReplayBuffer(
                args.buffer_size,
                len(train_envs),
                compute_reward_fn=compute_reward_fn,
                horizon=args.her_horizon,
                future_k=args.her_future_k,
            )
        else:
            buffer = HERReplayBuffer(
                args.buffer_size,
                compute_reward_fn=compute_reward_fn,
                horizon=args.her_horizon,
                future_k=args.her_future_k,
            )
    train_collector = Collector(policy, train_envs, buffer, exploration_noise=True)
    test_collector = Collector(policy, test_envs)
    train_collector.collect(n_step=args.start_timesteps, random=True)

    def save_best_fn(policy):
        torch.save(policy.state_dict(), os.path.join(log_path, "policy.pth"))

    if not args.watch:
        # trainer
        result = OffpolicyTrainer(
            policy=policy,
            train_collector=train_collector,
            test_collector=test_collector,
            max_epoch=args.epoch,
            step_per_epoch=args.step_per_epoch,
            step_per_collect=args.step_per_collect,
            episode_per_test=args.test_num,
            batch_size=args.batch_size,
            save_best_fn=save_best_fn,
            logger=logger,
            update_per_step=args.update_per_step,
            test_in_train=False,
        ).run()
        pprint.pprint(result)

    # Let's watch its performance!
    policy.eval()
    test_envs.seed(args.seed)
    test_collector.reset()
    result = test_collector.collect(n_episode=args.test_num, render=args.render)
    print(f'Final reward: {result["rews"].mean()}, length: {result["lens"].mean()}')


if __name__ == "__main__":
    test_ddpg()
